Goldilocks planet

Etymology
From the children's story Goldilocks, in which one of the bowls of porridge the protagonist tries is neither too hot nor too cold, but just right.

Noun

 * 1)  A planet which orbits in the habitable zone around a star, where temperatures like those on Earth occur, allowing for the possible existence of liquid water and of life.

Translations

 * Finnish: kultakutriplaneetta